/****************************************************************************
 *
 * Copyright 2016 Samsung Electronics All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific
 * language governing permissions and limitations under the License.
 *
 ****************************************************************************/
/****************************************************************************
 * kernel/environ/env_unsetenv.c
 *
 *   Copyright (C) 2007, 2009, 2011, 2013 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <tinyara/config.h>

#ifndef CONFIG_DISABLE_ENVIRON

#include <sched.h>
#include <string.h>
#include <errno.h>

#include <tinyara/kmalloc.h>

#include "sched/sched.h"
#include "environ/environ.h"

/****************************************************************************
 * Private Data
 ****************************************************************************/

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: unsetenv
 *
 * Description:
 *   The unsetenv() function deletes the variable name from the environment.
 *
 * Parameters:
 *   name - The name of the variable to delete
 *
 * Return Value:
 *   Zero on success
 *
 * Assumptions:
 *   Not called from an interrupt handler
 *
 ****************************************************************************/

int unsetenv(FAR const char *name)
{
	FAR struct tcb_s *rtcb = this_task();
	FAR struct task_group_s *group = rtcb->group;
	FAR char *pvar;
	FAR char *newenvp;
	int newsize;
	int ret = OK;

	DEBUGASSERT(name && group);

	/* Check if the variable exists */

	sched_lock();
	if (group && (pvar = env_findvar(group, name)) != NULL) {
		/* It does!  Remove the name=value pair from the environment. */

		(void)env_removevar(group, pvar);

		/* Reallocate the new environment buffer */

		newsize = group->tg_envsize;
		if (!rtcb->uheap) {
			newenvp = (FAR char *)kmm_realloc(group->tg_envp, newsize);
		} else {
			newenvp = (FAR char *)kumm_realloc(group->tg_envp, newsize);
		}

		if (!newenvp && (newsize != 0)) {
			set_errno(ENOMEM);
			ret = ERROR;
		} else {
			/* Save the new environment pointer (it might have changed due to
			 * reallocation.
			 */

			group->tg_envp = newenvp;
		}
	}

	sched_unlock();
	return ret;
}

#endif							/* CONFIG_DISABLE_ENVIRON */
